1. Field of the Invention
The present invention relates to a technology for sorting, binding, and stacking printed sheets discharged from an image forming apparatus.
2. Description of the Related Art
In a sheet processing apparatus that receives printed sheets fed from a discharging unit in an image forming apparatus provided outside or inside the sheet processing apparatus to stack these sheets on a staple tray and staples them into a bundle including a predetermined number of sheets by using a stapling unit to discharge this bundle to a paper discharge tray, a rear end of the sheet bundle is aligned by using a rear end fence on the staple tray to staple the bundle with an excellent accuracy or to convey the sheet bundle.
A sheet processing apparatus that pushes a front end of a sheet bundle toward a rear end fence side by using a rear surface of a discharge claw as a sheet bundle conveying unit that discharges the sheet bundle from a staple tray in a paper discharging direction, brings a rear end of the sheet bundle into contact with the rear end fence to align both the rear end and the front end, and conveys the aligned sheet bundle is proposed to improve alignment properties of the sheet bundle when aligning the rear end of the sheet bundle by using the rear end fence (see, for example, Japanese Patent Application Laid-open No. 2005-60106).
However, in the sheet processing apparatus according to Japanese Patent Application Laid-open No. 2005-60106, because the front end of the sheet bundle is pushed toward the rear end fence side by using the rear surface of the discharge claw when aligning the front end of the sheet bundle, the sheet bundle must be carried from the rear end fence by using the discharge claw and then moved to a position where the next sheet is received to enter a standby mode, and thereafter the sheet must be put into the staple tray. Therefore, this sheet processing apparatus has a problem that a waiting time until the sheet is put into the staple tray becomes long, thereby reducing productivity for producing the sheet bundles.